The prima facie speed limit declared for each street or portion thereof designated in section 12.20.020 of this chapter is a speed limit which is either an increase from the prima facie speed limit or a decrease from the maximum speed limit otherwise applicable to such street or portion thereof pursuant to California Vehicle Code, chapter 7 of division 11 commencing at section 22348 thereof. The increase or decrease has been determined upon the basis of an engineering and traffic survey. For each street or portion thereof upon which an increase in the prima facie speed limit (otherwise applicable) has been declared, a determination has been made that the increased declared prima facie speed limit is the most appropriate to facilitate the orderly movement of traffic and is reasonable and safe. For each street or portion thereof upon which a decrease from the maximum speed limit (otherwise applicable) has been made and a lower speed limit declared as the prima facie speed limit, a determination has been made that the maximum speed limit (otherwise applicable) is more than is reasonable or safe, and that the declared prima facie speed limit is most appropriate to facilitate the orderly movement of traffic and is reasonable and safe. (Ord. 27, 11-18-1992)